Science (1 19:2:51) When the skin is dry, the resistance of the body is lower than that of the skin

Science (1 19:2:51) When the skin is dry, the resistance of the body is lower than that of the skin

When sweating, the resistance of human body is low, and when the skin is dry, the resistance is high
When people sweat, there is a certain amount of salt in the sweat, which is equivalent to a layer of rare salt water on the surface of the skin, so the resistance is high
Similarly, when the skin is dry, the resistance is high

The gravity of a metal ball in the air measured by a spring dynamometer is 54n. When it is immersed in water, the indication of the spring dynamometer becomes 34n. The welfare of the metal ball is () n, and the volume of the metal ball is () m3 (G is 10N / kg)

The gravity of a metal ball in the air measured by a spring dynamometer is 54n. When it is immersed in water, the indication of the spring dynamometer becomes 34n. The buoyancy of the metal ball is [20] n. The volume of the metal ball is [0.002] cubic meters (G is 10N / kg). 1. F-float = G-F = 54n-34n = 20n2. F-float = ρ water GV row = 1.0 × 10 &

Science, mechanical movement (120:51:35)
① The speed ratio of the three students is 3:2:1, and the speed ratio of the three students is 3:2:1, so the time ratio of the three students to complete the same journey is as follows: the ratio of time required for them to complete the same distance is: the ratio of the speed of the three students is 3:2:1, and the time ratio of the three students to complete the same distance is: 160; (35;#####35;##35;35;#####################j###jjjjjj; 160; 160; 160;; ##it's not easy;
② From place a to place B, a person must travel at a speed of 4 m / s for the first 200 m, and must travel at a speed of 4 m / s for the first 200 m, then take a bus for the next 1000 m, and the speed is 10 m / s, then the average speed of the person is ###35;35;#35;35;35;35;###############j# ; 160; \############  ### #  \\160; & & 160; & & 160; & & 160; & & 160;
③ An object moving in a uniform rectrectrectrectrectrectmoving object, its distance in five seconds is 20 m, and its speed in the next two seconds is: if its distance in five seconds is 20 m, then its speed in the next two seconds is: the speed of the object in the second second second is: the speed of the object in the second second second second second is: the speed of the object in the second two seconds is: the speed of the object in the last two seconds is: the speed of 35; J \35;; 106;; \##j; \\#j;;; \#######j; 35\\\35; ;;;;;;;;;;;; \km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h; km / h
 
 

1. Because t = s / V, time is inversely proportional to speed when the distance is fixed, so we can see that the time ratio is 1:2:3
2. The average velocity is: v = s / T = 1200m / (200 / 4 + 1000 / 10) s = 8m / s
3. 4m / s, 14.4km/h